U.S. Pat. No. 3,986,659 issued Oct. 19, 1976, entitled "END CAPS FOR TUBULAR CONTAINERS", and U.S. Pat. No. 3,913,774 issued Oct. 21, 1975, entitled "END CAPS FOR CONTAINERS", relate to the packaging and tubular container art, wherein a tube having flexible sidewalls and normally formed of a thermo-plastic material approximately 0.005 to 0.02 inches in thickness, is held to a preformed or desired shape, as for instance a polygon, by rigid end caps. In the past, the rigid end caps have been coupled to the ends of the tube, i.e., to the flexible sides thereof, by use of adhesives, tape, staples and other fasteners. In the patents above, a flexible thermoplastic material such as polyvinyl chloride (PVC), oriented poly-styrene (OPS), or other flexible semi-rigid sheet material forms the basic stock material for the sides of the container or package. The sheets may be pre-extruded, extruded or calendered to a thickness of approximately 0.005 to 0.02 inches and adhesively joined along a longitudinal seam to form a tube. Additionally, the sheets or tubes may be creased along a predetermined number of edges to form a container with a polygonal cross-section, such as rectangle. A resultant, creased tubular stock member may be then cut into desired lengths, depending upon the size of the container to be fabricated, and perforations punched near the ends for permitting mechanical interlocking between end caps borne thereby and the ends of the container or package tube.
The end caps employed in the structures of the patents above are formed of a plastic material as by molding to create rigid end members, providing strength and rigidity to the entire container. The dimensions and shape of the end caps conform to the dimensions and shapes of the flexible sides of the tube. The end caps include a base portion substantially forming an end cover for the container tube and sidewalls. The end caps also have engaging means for interlocking with the perforations within the two flexible sides, i.e., projections extending outwardly of the sidewalls to achieve a positive mechanical lock for holding the end caps to the container or package.
As such, the package or container of the reference patents is uniquely assembleable by either hand or machine, since by mere insertion, the end cap locks to the tube without the need for adhesives, tapes, staples or other fasteners and without any secondary operation. Further, during the assembly process, the perforations and the projecting, engaging means are virtually self-aligning, completing the package or container when the end cap engaging means interlocks with the perforations.
While the tubular packages or containers, as set forth in the referred to patents, are sufficiently rigid, and permit the ready completion of the package by manual or machine projection of an end cap within the open end of the tube proper, and wherein the end caps are automatically locked to the ends of tube tube to achieve a relatively rigid container or package, the requirement to mold the end cap and the mass of material needed for the same, adds considerably to the overall costs of the container or package thus formed.
It is, therefore, a primary object of the present invention to provide an improved, low cost end cap for a tubular container which is formed from identical or similar plastic sheet material as the tube proper of the container or package.
It is a further object of the present invention to provide a low cost end cap for a tubular container or package which automatically locks upon being axially insertable into the end of the container or package tube, and which may be severed from a prefolded flexible semi-rigid strip of thermo-plastic material such that end caps of differing lengths may be formed from such basic stock material by simple severing the same transversely to required end cap length.